The i5-2500K is a second generation Sandy Bridge processor which is currently two generations old and nearly three years out of date. The many users that had the good sense to purchase this processor should feel in no hurry to upgrade as it's still no slouch, even by today's standards. The benchmark figures indicate that, even at stock clock rates, in terms of real-world performance this processor is approximately 20% slower than the best currently available, not bad considering its age. Given that the 2500K has an unlocked multiplier upping its performance by 10% with stock cooling should not pose much of a problem for the majority of owners. Here is a detailed performance comparison of the 2500K vs 4670K.
[Jul '13CPUPro]

The i7-8700K is Intel’s latest, top of the range, 8th generation Coffee Lake processor. Like Kaby Lake and Sky Lake before that, Coffee Lake is based on Intel’s 14nm architecture which has been slightly optimized on each iteration. Following AMD’s modus operandi, Intel has upped the cores and threads across the range of their CPUs. In previous generations, a 6-core processor would have been a high-end desk-top (HEDT) processor, however the i7-8700K is the first Intel CPU with 6 cores and 12 threads to be classified (and priced) as a mainstream consumer processor. Specifically, the i7-8700K features a base clock speed of 3.7 GHz which boosts to 4.7 GHz (4.5 GHz for the previous generation i7-7700k), 12MB of smart (L3) cache and 2 channels of DDR4 RAM. The majority of the performance improvements over the 7th generation stem from the higher core count which results in a 50% increase in multi-core speed between the i7-7700k and i7-8700k. A new motherboard will need to be factored into the budget when upgrading to the 8700K as it requires a new Intel Z370 chipset which has supposedly been designed to better deliver power to CPUs with a greater number of cores. Also available in this latest release of CPUs is the 6 core 6 thread i5-8600k which is a more rational option (around $100 cheaper) for the vast majority of users that don’t require hyper-threading. Sandy bridge owners can finally justify an upgrade but with the next iteration of AMD's Zen architecture just around the corner the CPU market will be a lot faster moving now that Intel, once again, has to compete. [Sep '17CPUPro]

CHOOSE A COMPONENT:

We calculate effective speed which measures real world performance for typical consumers. Effective speed is adjusted by current prices to yield a value for money rating which is geared towards gamers. Our calculated values are checked against thousands of individual user ratings. The customizable table below combines these factors to bring you the definitive list of top CPUs. [CPUPro]

Welcome to our freeware PC speed test tool. UserBenchmark will test your PC and compare the results to other users with the same components. You can quickly size up your PC, identify hardware problems and explore the best upgrades.